1. Field of the Invention
This invention relates generally to the utilization of solar energy for heating purposes and more particularly to a novel cascade storage method of and apparatus for utilizing solar energy to augment the heater of a water heating system, such as a domestic hot water system.
2. Prior Art
At the present time, there is an ever increasing trend in the direction of solar energy utilization for both electrical power generating and heating purposes. This invention is concerned wih utilizing solar energy for heating purposes and more particularly for augmenting the heater of a water heating system of the kind having a water storage and heating tank. A common example of such a heating system is a domestic hot water system. This invention is primarily concerned with and will be described in the context of such a domestic hot water system.
A conventional domestic hot water system includes a water heater having a heating tank with a water inlet connected to the city water supply and an outlet connected to a hot water service line. Within the tank is a water heater, such as a gas burner or electrical heating element, which is controlled by a thermostat in the tank in such a way that the heater turns off when the water in the tank reaches a preset maximum set point temperature and on when the water cools to a lower minimum set point temperature. In normal heater operation, the heater cycles on and off in response to hot water consumption and heat loss from the heater tank.
It is known to utilize solar energy to augment the heat source of such a hot water system and thereby reduce the energy consumption of the system. By way of example, U.S. Pat. No. 1,888,620 describes such a solar energy augmented hot water system. Other solar energy augmented heating systems are described in U.S. Pat. Nos. 2,575,478; 2,396,338; 3,152,442; and 2,713,252.